Coordination-Induced Trigger for Activity: N-Heterocyclic Carbene-Decorated Ceria Catalysts Incorporating Cr and Rh with Activity Induction by Surface Adsorption Site Control

Abstract

A coordination-induced trigger for catalytic activity is proposed on an N-heterocyclic carbene (NHC)-decorated ceria catalyst incorporating Cr and Rh (ICy-r-Cr0.19Rh0.06CeO z ). ICy-r-Cr0.19Rh0.06CeO z was prepared by grafting 1,3-dicyclohexylimidazol-2-ylidene (ICy) onto H2-reduced Cr0.19Rh0.06CeO z (r-Cr0.19Rh0.06CeO z ) surfaces, which went on to exhibit substantial catalytic activity for the 1,4-arylation of cyclohexenone with phenylboronic acid, whereas r-Cr0.19Rh0.06CeO z without ICy was inactive. FT-IR, Rh K-edge XAFS, XPS, and photoluminescence spectroscopy showed that the ICy carbene-coordinated Rh nanoclusters were the key active species. The coordination-induced trigger for catalytic activity on the ICy-bearing Rh nanoclusters could not be attributed to electronic donation from ICy to the Rh nanoclusters. DFT calculations suggested that ICy controlled the adsorption sites of the phenyl group on the Rh nanocluster to promote the C–C bond formation of the phenyl group and cyclohexenone.

Low-temperature redox activity and alcohol ammoxidation performance on Cu- and Ru-incorporated ceria catalysts

“…13 We reported that Cr-and Rh-incorporated ceria, Cr 0.19 Rh 0.06 CeO z , showed superior redox performance at low temperatures (o373 K) compared with pure ceria. [14][15][16] Cr 0.19 Rh 0.06 CeO z exhibited the redox performance of all three metal species and had remarkable NO reduction performance toward N 2 because Rh activated the CO and NO species and Cr cleaved NO species. 14,15 Thus, incorporating multiple metal species into ceria surface leads to efficient oxidation catalysis.…”

Geometric and Electronic Effects in the Binding Affinity of Imidazole-Based N-Heterocyclic Carbenes to Cu(100)- and Ag(100)-Based Pd and Pt Single-Atom Alloy Surfaces

“…Molecular corks can also affect the structure and reactivity of catalytic metal surfaces. − ,,,− Recently, the use of CO on Pd/Au(111) SAAs to modify the active sites of SAA catalysts has been demonstrated via density function theory (DFT) calculations and then confirmed via experiment . DFT studies have shown the ability of CO to influence the morphology of 15 distinct SAAs .…”

NMR Spectroscopic Signatures of Cationic Surface Sites from Supported Coinage Metals Interacting with N-Heterocyclic Carbenes

“…In parallel to these fundamental studies in surface science, NHCs have been introduced on both colloids and supported nanoparticles (NPs) to modulate their catalytic performances. ,,− In these reports, the binding of NHC ligands on the metal surface is proposed to adopt a vertical monocoordinated NHC configuration. , Detailed nuclear magnetic resonance (NMR) spectroscopic investigations of silica-supported Cu species have shown that the spectroscopic signatures could in principle help to distinguish various surface sites, in particular, NHC adsorbed on isolated metal surface sites vs metallic surface sites from protonated imidazolium species (Figure b) . Nonetheless, bis-NHC metal cationic surface sites have so far not been considered on coinage metal supported on oxide surfaces, raising questions about their existence and specific (NMR) spectroscopic signatures.…”